Helix seam for woven papermaking dryer fabrics

ABSTRACT

A stitched seam for high-tensile woven fabric strips, in particular for dryer screen fabric for paper machine clothing, wherein the warp thread loops of the two fabric sections to be interconnected are connected at the location of the common seam by a closure wire. At least one of the two outer regions of the two fabric strip sections to be interconnected comprises a worked-in helix at the location of the seam. Each of the helices embraces at least one weft thread and the closure thread. The other region of the stitched seam of the ends of the two fabric strip sections consists of the loops formed by the warp threads of the fabric.

BACKGROUND

The invention relates to a stitched seam for high-tensile woven fabricsespecially for dryer fabric for paper machine clothing in which the warpyarn loops of the two fabric sections to be interconnected are connectedtogether at the location of the common seam by means of a closure wire.

In so-called loop stitch seams the fabric edge is basically that portionwhich is subjected to the greatest stress. If excessive tensions arecreated in the fabric, there frequently occurs in those portions aso-called eyelet rupture, which requires repair or replacement of thefabric.

The object of the invention is to strengthen this weak spot and therebyprevent the risk of an eyelet rupture, or at least reduce it, andthereby increase the life span of such fabrics.

This object is achieved in accordance with the invention by providing atleast one of the two outer regions of the two fabric sections which areto be interconnected at the seam location with at least one worked-inhelix, while the remaining portion of the stitched seam at the ends ofthe two fabric sections consists of the loops formed by the warp yarnsof the fabric.

Further embodiments of the invention are the subject of the dependentclaims.

SUMMARY

The stitched seam constituting the invention consists essentially of anextraneous material which takes the shape of a helix and is worked intoat least one, but generally into both edge portions of the two fabricsections. In this way there is created a stitched seam which consists oftwo different seam systems and which results in strengthening preciselythe weak spots, namely the outer regions of the fabric. In contrast to aconventional loop seam, in which only every second yarn can be used as aconnecting yarn, so that the seam strength is approximately 50% of thefabric tear strength, by using a seam reinforcement in accordance withthe invention, the helices are held in by all the warp yarns so that asubstantial increase in seam tear strength is achieved compared to aloop seam. In so doing, the tear strength is primarily a function of thestrength of the helices, i.e., their diameter and their materialproperties.

The helix configuration is such that a helix is worked into each of theleft and right edge portions of the confronting free ends of the twofabric sections. At the locations of the helices the warp yarnsprotrude, in loop shape, equally far into the end region, whereas, inthe remaining portion of the fabric web, they are displaced with respectto each other in the lengthwise direction in conventional manner and theloops of the two fabric sections alternately protrude differently far,so that only every second loop of each of the two fabric sectionsencircles the connecting wire.

The ends of the two helices in the two fabric sections are attachedtoward the fabric center. At the edge, the respective helix end portionis straightened and pulled back toward the fabric and at the transitionfrom the loop seam a straightened piece is worked in so that the helixends cannot be pulled out. The working-in of the helices can take placeat the same time as the production of the loop seam but it is alsoreadily possible to work the helices in separately at a later time.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows the invention is explained with reference to the drawingby means of illustrative examples. There is shown in

FIG. 1 an illustration in principle of the stitched seam according tothe invention, in open position,

FIG. 1a an illustration in principle corresponding to FIG. 1 in closedposition,

FIG. 2 a detailed illustration of a segment of the seam construction inaccordance with the invention in the closed position, seen from above,

FIG. 3 an illustration of the stitched seam in the form of a circularfragment of FIG. 2, but only the stitched seam portion of fabric section1,

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the ends of two fabric sections 1 and 2, which areconnected to each other by a common stitched seam 3. The stitched seam 3consists of several parts and has in each of the two fabric sections aloop stitch seam 4, 4' in the center portion of each fabric section, aswell as a reinforcing helix seam 5, 6, 5', 6' at the two outer regionsof each fabric section. The closure wire which passes through both seamsystems and the seam connections 4-6, 4'-6' is designated by thereference numeral 7.

The warp yarns of fabric section 1 are designated as 8, 8a, 8b, 8c . . .in FIGS. 2 and 3, the warp yarns of the fabric section 2 are designatedas 9, 9a, 9b, 9c . . . , the warp yarns of fabric section 1 as 10, 10a,10b . . . and the warp yarns of fabric section 2 as 11, 11a, 11b . . . .

Helix 12 of helix seam connection 5 is worked into fabric section 1,helix 13 into fabric section 2. In the separate fabric sections whichare to be connected to each other, the loops of helices 12 and 13 arelocated in each other's interstices and overlap in the lengthwisedirection of the fabric web sufficiently that the connecting wire 7 canpass through the loops of both helices 12 and 13; at the same time, inthe remaining portion of the fabric web (outside the helix structure)which takes the form of a conventional loop seam, this connecting wire 7passes alternately through the loops of adjoining parallel warp yarns,as shown in detail in FIG. 2. The helix ends take the form of extensions14, 15 of helices 12, 13 and, after the end portion of each helix isstraightened out and pulled back toward the fabric, are attached in theinterior of the fabric by means of the lengthwise yarns. Preferably thehelices 5 and 6 are worked in simultaneously with the loop seam 4, sothat they form an initial component of the fabric sections 1 and 2 whichare to be interconnected. However, optionally, they could also be workedin separately, at a later time.

Helices 12 and 13 embrace within their loops the common connecting wire7 which, in the area of the helix-reinforced seam connection 3, passes,respectively, through one turn of helix 12 and one of helix 13, theturns of helices 12, 13 being arranged, for example, in each other'sinterstices to provide the connection of the two fabric sections 1 and 2in the area of reinforcement, in place of the loops of the warp yarns ofthe two sections 1 and 2. The loop seam in the remaining portion of theseam connection of the fabric web is formed in conventional manner. Inso doing, each helix 12 and 13 encloses the closure wire 7 and one crossmachine direction (CMD) yarn 10 or several cross machine direction yarns10, 10a, 10b.

Each helix is preferably manufactured from polyetheretherkeytone (PEEK),polyphenylere sulfide (PPS), polyethylene terephthalate (PET), polyamide(PA), polycarbonate (PC), aramide, metal or the like and is preferablymatched to the materials used for the fabric.

I claim:
 1. A stitched seam for a fabric web including interwoven warpand weft yarns defining opposed ends and opposed edges, the warp yarnsdefining yarn loops at each end of the fabric to be interconnected at acommon connection location by means of a closure wire, the seamcharacterized in that at least a portion of each end of the fabric isprovided with a worked-in helix, each of the helices enclosing at leastone weft yarn and defining at least one helix loop adjacent therespective yarn loops, such that a closure wire channel that includes aplurality of yarn loops and at least one helix loop is defined at eachend of the fabric, whereby the channels are aligned and the closure wireinserted through the yarn loops and helix loops to seam the fabric. 2.Stitched seam according to claim 1 characterized in that a worked-inhelix is provided adjacent each fabric edge and the remainder of eachchannel between the two worked-in helices consists of yarn loops. 3.Stitched seam according to claim 1, characterized in that each helixconsists of polyetheretherkeytone (PEEK), polyphenylere sulfide (PPS),polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC),aramide, metal or the like and is matched to the materials used for thefabric.
 4. Stitched seam according to claim 1 further characterized inhelix loops of one end of the fabric alternating with helix loops of theother end of the fabric when the channels are aligned.
 5. Stitched seamaccording to claim 1 further characterized by each portion of the fabricprovided with a worked-in helix including at least two adjacent helixloops.
 6. Stitched seam according to claim 5 further characterized inthat at least two warp yarns are positioned between adjacent helixloops.